For at least the past fifty years, there has been an interest in the possibilities of enhancing seed performance, particularly with respect to improved germination and seedling establishment. Seed treatments that initiate or complete the germination process under controlled conditions prior to sowing would possess a number of practical advantages, particularly if germination could be both synchronized and accelerated. Rapid establishment of a uniform population of seedlings improves the ability of the crop to compete with weeds, and further economies result from the management of a uniform population of plants, including enhanced uniformity of the yield at harvest. Rapid germination following sowing can reduce erosion by rapidly stabilizing denuded slopes and can bring playing fields such as golf greens to playable levels in shorter times, using less seed. Rapid germination can reduce the exposure of the planted seed to infection, thus reducing the need for extensive chemical control of conditions such as damping off. In fact, the time from seeding to harvest for a given crop could be effectively shortened by at least the number of days normally required for germination in the soil.
Attempts to accelerate germination have included the use of physical or chemical treatments intended to shorten the dormancy period following seed formation. Such treatments include exposure of seed to light, exposure of seed to cool moist conditions (stratification), mechanical scarification, treatment with chemical agents such as gibberellic acid, potassium nitrate, thiourea, hydrogen peroxide or ethylene, seed hardening, and osmotic priming.
Controlling seed hydration can influence the timing and synchronization of germination. The known methods for control of hydration limit the amount water available to the seed during hydration. For example, in osmotic priming, seeds are exposed to polyethylene glycol in an aqueous solution which acts to decrease the amount of water available to the seed during hydration. Generally, subsequent drying reduces the degree of advancement or synchronization obtained by osmotic priming.
Seed hardening treatments involve allowing the seeds to take up water followed by drying them back to near the original moisture content. Water uptake is limited by the imbibition time or quantity of water made available to the seed. Seeds are dried back to near their original moisture contents by air drying, drying with heat or freeze drying, so that seeds can be stored without deterioration.
There is a varied response to seed hardening. In some cases, drying back eliminates the beneficial effects of pregermination hydration treatments so that germination is delayed and desynchronized like that seen in untreated seeds. In other cases, dehydration can lead to secondary dormancy or even damage to the embryo. Seed hardening, when successful, usually only shortens germination time by days.
Therefore, it is an object of the present invention to decrease the germination time of seeds following planting and at the same time to increase synchronous germination of the seeds.
It is a further object of this invention to obtain seeds that are capable of rapid synchronous germination in a consistent manner following storage under ambient humidities.